1. Technical Field
Various embodiments of the present disclosure relate to photo masks used in a lithography process and, more particularly, to photo masks including pre-alignment keys and photolithography apparatuses performing a pre-alignment process for the photo masks.
2. Related Art
In general, a photo mask is located between a wafer and a light source in a photolithography apparatus to perform a photolithography process for transferring circuit patterns of the photo mask onto the wafer. In order to perform the photolithography process, the photo mask may be loaded on a stage in the photolithography apparatus. In such a case, it may be very important to accurately load the photo mask on a predetermined position of the stage. This is because alignment accuracy in the photolithography process depends on the position of the photo mask. The position of the photo mask loaded on the stage may be controlled by a pre-alignment process.